StateFile: configurable interval

doc/user.xml

@@ -898,6 +898,18 @@ systemctl start mpd.socket</programlisting>
                   (<parameter>+wx</parameter>).
                 </entry>
               </row>
+
+              <row>
+                <entry>
+                  <varname>state_file_interval</varname>
+                  <parameter>SECONDS</parameter>
+                </entry>
+                <entry>
+                  Auto-save the state file this number of seconds
+                  after each state change.  Defaults to
+                  <parameter>120</parameter> (2 minutes).
+                </entry>
+              </row>
             </tbody>
           </tgroup>
         </informaltable>

src/Main.cxx

@@ -279,7 +279,10 @@ glue_state_file_init(Error &error)
 #endif
 	}
 
-	state_file = new StateFile(std::move(path_fs),
+	unsigned interval = config_get_unsigned(CONF_STATE_FILE_INTERVAL,
+						StateFile::DEFAULT_INTERVAL);
+
+	state_file = new StateFile(std::move(path_fs), interval,
 				   *instance->partition,
 				   *instance->event_loop);
 	state_file->Read();

src/StateFile.cxx

@@ -36,10 +36,11 @@
 
 static constexpr Domain state_file_domain("state_file");
 
-StateFile::StateFile(AllocatedPath &&_path,
+StateFile::StateFile(AllocatedPath &&_path, unsigned _interval,
 		     Partition &_partition, EventLoop &_loop)
 	:TimeoutMonitor(_loop),
 	 path(std::move(_path)), path_utf8(path.ToUTF8()),
+	 interval(_interval),
 	 partition(_partition),
 	 prev_volume_version(0), prev_output_version(0),
 	 prev_playlist_version(0)
@@ -137,7 +138,7 @@ void
 StateFile::CheckModified()
 {
 	if (!IsActive() && IsModified())
-		ScheduleSeconds(2 * 60);
+		ScheduleSeconds(interval);
 }
 
 void

src/StateFile.hxx

@@ -34,6 +34,8 @@ class StateFile final : private TimeoutMonitor {
 	const AllocatedPath path;
 	const std::string path_utf8;
 
+	const unsigned interval;
+
 	Partition &partition;
 
 	/**
@@ -44,7 +46,10 @@ class StateFile final : private TimeoutMonitor {
 		prev_playlist_version;
 
 public:
-	StateFile(AllocatedPath &&path, Partition &partition, EventLoop &loop);
+	static constexpr unsigned DEFAULT_INTERVAL = 2 * 60;
+
+	StateFile(AllocatedPath &&path, unsigned interval,
+		  Partition &partition, EventLoop &loop);
 
 	void Read();
 	void Write();

src/config/ConfigOption.hxx

@@ -32,6 +32,7 @@ enum ConfigOption {
 	CONF_LOG_FILE,
 	CONF_PID_FILE,
 	CONF_STATE_FILE,
+	CONF_STATE_FILE_INTERVAL,
 	CONF_RESTORE_PAUSED,
 	CONF_USER,
 	CONF_GROUP,

src/config/ConfigTemplates.cxx

@@ -32,6 +32,7 @@ const ConfigTemplate config_templates[] = {
 	{ "log_file", false, false },
 	{ "pid_file", false, false },
 	{ "state_file", false, false },
+	{ "state_file_interval", false, false },
 	{ "restore_paused", false, false },
 	{ "user", false, false },
 	{ "group", false, false },